Two-stroke internal combustion engine



April 1938- H. J; VENEDIGER 2,115,657

TWO-STROKE INTERNAL COMBUSTION ENGINE Filed April 9, 1936 2 Sheets-Sheet l April 6, 1938. H. J.VENEDIGER 1 2,115,657

TWO-STROKE INTERNAL COMBUSTION ENGINE Filed April 9 1936 2 Sheets-Sheet 2 Patented Apr. 26 1933 UNITED .STATES" Si nor to Auto Chemnitz, Germany Application In 5 Claims.

This invention relates to a two-stroke internal combustion engine with port scavenging, in which the scavenging and inlet-ports are arranged on both sides oithe outlet ports placed side by side and lie at about the same height.

Engines with outlet and scavenging ports in such position are known. In the known engines however, the arrangement is such that the various scavenging passages conduct the scavengingair against the cylinder wall lying opposite the outlet passages. g ,2

These engines have a number of disadvantages. In the case of mixture compressing engines they have high fuel consumption, unsatisfactory running with throttle control, non-uniform heating of the cylinder and piston parts and the like, as a result of inadequate scavenging. a In .the accompanying drawings Figs. 1-4 show a two-stroke internal combustion engine of a possible (Fig. 1) or of a hitherto known (Figs. 2-4) construction. Figs. 1-3 are cross-sections through the zones of the control passages arranged at the same dead centrepolnt, and Fig. 4 is a longitudinal section of the cylinder. Figs. 5 to l are cross sections through a cylinderaccorda ing to the invention, the section being taken' at the height of the exhaust and scavenging ports,

- and these figures include a plan view of the piston head and diagrammatic illustrations of the paths of scavenging. Figure 8=is a longitudinal section of the cylinder shown in Figures 5' to '7. a

, Figure 9 is a cross section through a cylinder in which the scavenging ports have a difierent positionaseompared with the scavenging ports of -Figures 5 to 7. Figure 10 is a partial section through the cylinder with side elevation of the piston. Figure 11 is a longitudinal section through a cylinder with additional scavenging portsjin. the rear cylinder wall. Figure 12 is a cross section through the cylinder shown-in Figure 11 at the height of the. exhaust and scavenging ports. Figures 13 to 15 are cross sectional views similar to Figure 11, in which the additional scavenging ports' are designed difl'erently.

- Two outlet passages A1, A: .and two scavenging passages S1, Sz-are assumed by way of example. Fig. 1 shows a possible arrangement of the scavenging passages S1, S2, which is so chosen'that the scavenging jets l, 2 flowing through the scavenging passages meet at about thecentre of the{ cylinder.

In'Fig. 2, the jets I, 2 'met, for example,

at the rear cylinder wall m, but in Fig. ac: count of the greater inclination of the passages, they meet on .theother side of the cylinder wall April 9, 1936, Serial Germany April 9, 1935 are two such zones, but in Fig. 3 the steeply are the scavenging passages inclined.

TERNAL oormus'rlon ENGINE I Herbert Jose! Venediger, Chemnitz.

Germany, 88'' Union Aktiengeselischatt.

m. The breadth of the scavenging streams due to the breadth-oi the passages are shown in Figs. 1-3 in broken lines. v Even it actually the scavenging stream'entering the cylinder expands laterally there will still 5 be considerable parts of the cylinder unscavenged, as shown in Figs. 1-3, where the unscavenged zones adjoining the cylinder wall (11 are indicated with horizontal hatching, and the zones enclosed by the scavenging streams and also re- 10 .maining unscaveng'ed, are indicated byvcrosshatching. The horizontally hatched zone indicated by 3 is greatest in Fig. 1; in Fig. 2 there zone 3 is very small and in view of the lateral expansion of the 15 scavenging stream, is negligible. 7

Figs. 2: and 3 show a cross-hatched residual gas zone 4, which is absentin Fig. 1, but is great.- est in Fig. 3. In order to understand this zone 4 reference is made to Fig. 4 showing the arrange- 2o ment of the scavenging passages S1, S2 according to Fig. 2. The longitudinal section (Fig; 4) isso taken that it passes through the outlet passage The scavenging stream entering through the scavenging passage S1 is indicated by l as 25 long as it is moving upwards towards the cylinder head and with I. when itflows downwards again to the piston b. The same applies for the and l", .2" lies the residual gas zone 4,. Above the piston b and near the rear cylinder wall or there isformed a further piston end zone 5, not hitherto mentioned. This is greater the more35 The above explanation makes the principal disadvantages of this known scavenging operation clear. At the same time the known uniform heating of the piston and cylinder wall is made clear. The more acute is the angle p enclosed by the scavenging streams l, 2, the smaller is the central loss oi. scavenging duet direct escape into the outlet passages (short circuit), but the greater the residual gas zone I, see Figs. l-ii so' that in general when the zone 3 decreases the zone 4 increases, and vice versa. The zone 5 is greater the greater is the angle between the scavenging passages and the horizontalplane.

.The hitherto known engines with. the above identified port arrangement, that is accordingto Figs. 2 and 3, use a flat or slightly arched piston I head andleave the guiding of-the scavenging streams exclusively to the scavenging passage and the rear cylinder wall. g a

The invention beginsirom the fact that in this wayacomplete scavenging cannot be obtained and that in fact no scavenging operation can dispense with the guiding of the scavenging streams by the piston or other suitable guiding devices. It also goes a substantial step further and imposes the requirement for which it also gives the solution, thatthe directive actionon the scavenging streams through the scavenging operation must be variable in such a manner that the scavenging operation shown in Figs. 14 must be carried through continuously as phases of the scavenging. The scavenging streams l, 2 must therefore first be so mutually directed for the purpose of avoiding the zones 3 that they would first meet on the far side of the rear cylinder wall m (Fig. 3), then a part of the scavenging streams must flow in such a manner as shown in Fig. 2 that the residual gas zone 4 is diminished, and finally further part streams must be split 011 in such a manner that they meet approximately in the centre of the cylinder, as shown in Fig. 1, so as to remove the residual gas zone 4 entirely.

This is carried into eifect according to the constructional example of the invention by the scavenging passages according to the invention being directed approximately towards the centre of the cylinder and by the piston b having a symmetrically shaped guiding device which continually deflects the scavenging streams l, 2 during the scavenging operation.

For this purpose the piston head is fitted with a disc-like plate which is substantially bellshaped in outline and the height of which diminishes in the direction of the outlet passages. The boundary curves e1, e: of the outline are preferably connected together by a rounded part which is preferably approximately semi-circular.

Figs. 5-7 each show cross-sections through the cylinder passing through the outlet passages A1, A: and the scavenging passages 81, S: with a plan view of the piston. Fig. 8 shows a longitudinal section through the cylinder and piston, with a diagrammatic illustration of the scavenging operation according to the invention. This is divided, according to the invention, into the following three principal stages:

First stage, according to Figs. 5 and 8 The working of the piston b with guide device' 0 causes the scavenging passages 81, B2 to be opened to such an extent that scavenging medium (air, fuel-air-mixture, combustible gases) can enter into the cylinder according to its pressure. The scavenging medium is deflected without shock against the rear cylinder wall a: by the guide device c in i such a manner that the middle scavenging streams I, 2 would meet on the far side of the 'rear cylinder wall. They then flow along the rear cylinder wall upwardly to the cylinder head and from there in the direction towards the outlet es A1, A2, as illustrated in Fig. 8.

Second stage, according to Figs. 6 and 8 The working piston is now in front of the lower dead centre position. Since the greatest height of the guiding device according to the invention is preferably about as great as the greatest height of the scavenging passages, a part of the scavenging medium now flows over the guiding device at the points where the height of the guiding de vice is smaller than that of the scavenging ports. These part streams lb, 2b are thus deflected to a less extent than the part streams la, 2a, which together with the streams lb, 21) form the whole scavenging stream l, 2. They therefore take approximately the direction shown in Figs. 6 and 8. When flowing upwards towards the cylinder head they remove for the most part the residual gas zone 4 remaining from the first stage of the scavenging. The small amount of residual gas 1 then remaining is indicated by cross hatching in Fig. 2.

Third stage, according to Figs. 7 and 8 The working piston is now in the lower dead centre position. A part of the scavenging medium flows as described in the first stage; a further part flows as in the second stage, while the remaining part flows towards the centre of the cylinden without any noticeable deflection by the guide device, forming part streams lo, 20, and then flows to the cylinder head. By this means the small amount of exhaust gas remaining from the second stage is completely driven out. I

When the piston b moves back (upward stroke) the three stages are repeated in the reverse sequence. The reversing of the sequence is very important because by this means the scavenging streams are guided towards the rear cylinder wall and kept away from the outlet. Thus according to the invention satisfactory scavenging is obtained, while the outflow losses are diminished.

The heights of the guiding device 0 of the piston are made greater the greater is the angle which the scavenging passages make with the horizontal plane. The rear cylinder wall need not be continuous as in the example. Further scavenging and inlet ports may be provided there, which at the best will open into the cylinder with a steep upward inclination. Their streams will then preferably extend in such a manner that they assist the part currents la and 2a and lb and 21).

According to the invention the shape and distribution of mass of the guide device 0 is so chosen that the centre of gravity thereof falls in the axis of the cylinder. By this means a tilting of the piston is avoided.

In order to obtain a piston as light as possible, according to the invention, the parts b1 adjoining the outlet ports are made plane and the guide device a is made dove-tailed as shown in Fig. 9 by' way of example, where the guide device consists only of two intersected webs. In this way a working piston can be obtained, the weight and surface of which are scarcely greater than those of a fiat piston without guide device; also the combustion space of the engine can be shaped as desired.

- Figs. 11-15 of the drawings show furtherconstructional example of the engine according to the. invention in which the rear cylinder wall a1 has further scavenging or inlet ports opening into it preferably with steep upward inclination, the streams of which serve for improving the cylinder'filling or scavenging, preferably for setting up and assisting the streams coming from the other scavenging passages. In Fig. 12, which is a cross-section of Fig. 11, there is provided in the rear cylinder wall 411 a single scavenging Passage 8: with steep upward inclination,- the stream from which combines with the part streams la from the scavenging passages S1 and S1. In Figs. 13 to 15 further preferred constructional forms are illustrated in which the streams coming from the scavenging passages S; and S4 and flowing to the cylinderhead improve the stability of the total stream.

The invention is suitable for two-stroke mixture engines and two-stroke Diesel engines, and

is used with advantage both. tor. crank case engines and for engines with separate charging pumps. In the figures the scavenging passages are shown equally high. Instead of this they can be constructed with diminishing heights, as shown in Fig. 10. According to the invention the upper controlling edge should fall away to r the same extent as the height of the guide device 0. In this way the scavenging streamsadapt themselves very satisfactorily to the cylinder space to be scavenged.

What I claim is:-

1. In a two-stroke internal combustion engine, a cylinder wall having an outlet passage therein, said wall having inlet passages symmetrically arranged on each side of said outlet passage and at the same height, the axes of said inlet passages meeting substantially in the axis of said cylinder, a piston,'a disc-like guide device of bellshaped outline in plan decreasing in height from a point adjacent the inlet passages towards the outlet passages and located on the head of said piston, the upper controlling edges of the inlet passages decreasing in the same degree as the height of the guide device carried on said piston.

2. An internal combustion engine as claimed in claim 1 in which the guide device extends up to the part of a cylinder wall opposite the outlet passages.

3. In a two-stroke internal combustion engine, a cylinder wall having scavenging ports, a piston in said cylinder controlling the scavenging port, said cylinder having exhaust ports, and said scavenging ports being arranged on both sides of the exhaust ports, a guide device having bellshaped plan on the head of said piston with the highest parts at the vertex of the bell and diminishing in height towards the base of the bell, said base being adjacent the exhaust ports .when the piston is at the bottom of its stroke, the edge of the bell-shaped guide device at the periphery ot the piston being at least as wide as the part of the inner cylinder wall occupied by the exhaust ports and narrower than the part of the inner cylinder wall occupied by the scavenging ports. A I

4. An internal combustion engine as set forth in claim 3 in which the part of a cylinder wall opposite the exhaust ports is provided with additional scavenging and inlet steeply inclined upwardly.

5. An internal-combustion engine as claimed in claim 3; in which the greatest heightof the guide device is substantially as great as the height of the scavenging ports.

HER-BERT JOSEF 'vnnnmann.

ports which, are 

